1. Field of the Invention
The present invention relates to an actinic-ray- or radiation-sensitive resin composition and a method of forming a pattern using the same. More specifically, the present invention relates to a composition and a method of forming a pattern therewith that is suitable for use in lithography operations employed in a semiconductor production process for an IC or the like, the production of a circuit board for a liquid crystal, a thermal head or the like and other photofabrication. Further more specifically, the present invention relates to a composition and a method of forming a pattern therewith that is suitable for exposure using an a far-ultraviolet light of wavelength 250 nm or shorter or an electron beam as a light source.
In the present invention, the terms “actinic rays” and “radiation” mean, for example, a mercury lamp bright line spectrum, far ultraviolet rays represented by an excimer laser, extreme ultraviolet (EUV) rays, X-rays, electron beams (EB) and the like. In the present invention, the term “light” means actinic rays or radiation.
The expression “exposure” used herein, unless otherwise noted, means not only light irradiation using a mercury lamp, far ultraviolet, X-rays, EUV light, etc. but also lithography using particle beams, such as an electron beam and an ion beam.
2. Description of the Related Art
A chemical amplification resist is a material for forming a pattern capable of, upon exposure to far ultraviolet rays or other radiation, generating an acid at the exposed area. A reaction catalyzed by the generated acid allow the solubility of the exposed area in a developer to be different from that of the non-exposed area. The difference in the solubility between those areas makes it possible to attain pattern formation on a substrate.
In using a KrF excimer laser as an exposure light source, a resin whose fundamental skeleton consists of a poly(hydroxystyrene) exhibiting a low absorption mainly in the region of 248 nm is employed as a major component. Accordingly, favorable pattern with high sensitivity and high resolving power can be formed. Thus, a system superior to the conventional naphthoquinone diazide/novolak resin system has been realized.
On the other hand, in using a light source of a further shorter wavelength, for example, an ArF excimer laser (193 nm) as an exposure light source, the above-mentioned chemical amplification system has not been satisfactory because the compounds having an aromatic group inherently exhibit a sharp absorption in the region around 193 nm.
Therefore, various resists for an ArF excimer laser containing an alicyclic hydrocarbon structure have been developed. However, the current situation is that it is extremely difficult to discover an appropriate combination among an employed resin, a photoacid generator, an additive and a solvent, etc., from the viewpoint of the comprehensive performance of a resist. In particular, in the formation of a nanopattern of 65 nm or less line width, there is a demand for enhancing the line pattern roughness performance and resolving power
In recent years, it has been discovered that the resolving power, roughness characteristics and pattern collapse performance can be improved by making the above resin with an alicyclic hydrocarbon structure contain a repeating unit with a specified lactone structure or a specified alcohol structure having its α-position substituted with a fluoroalkyl group.
For example, patent references 1 and 2 describe resist compositions each loaded with a resin containing a repeating unit with a structure in which a spacer is introduced between a polymer principal chain and a lactone skeleton. Further, patent reference 3 describes that not only the resolving power and line edge roughness but also the iso/dense bias and exposure margin can be improved by using resist compositions each loaded with a resin containing a specified lactone repeating unit in which a similar spacer is introduced.
Still further, patent references 4 and 5 describe resist compositions each loaded with a resin containing a repeating unit with a specified alcohol structure having its α-position substituted with a fluoroalkyl group. It is also described that the roughness characteristics and pattern collapse performance can be improved by the use of such resist compositions.
Various ingenuities have also been exerted on other components than the resin. For example, patent reference 6 describes that a specified low-molecular compound whose proton acceptor properties are dissipated upon exposure to light is effective in the improvement of roughness performance.
However, in the most recent 45 nm or less line width generation to which a liquid immersion process is applied, it is required to further enhance the resist performances. In particular, it is required to further enhance not only the line width roughness (LWR) and pattern collapse performance but also the defocus latitude (Depth of Focus: DOF).
[Citation List]
[Patent Literature]
[Patent reference 1] Jpn. Pat. Appln. KOKAI Publication No. (hereinafter referred to as JP-A-) 2005-352466,
[Patent reference 2] JP-A-2004-210917,
[Patent reference 3] JP-A-2008-031298,
[Patent reference 4] JP-A-2007-119678,
[Patent reference 5] JP-A-2005-321765, and
[Patent reference 6] JP-A-2006-330098.